It's a ridiculous analogy for sure. The player wants to leave to a more successful club, that's all there is to it. It's unfortunate, but these things happen. Not all players want to stay at their home club when presented with a better career move. It happened before with the Michael Owen transfer. Also with Beckham to a lesser degree.
Liverpool fans are angry because they hoped Arnold would prioritize Liverpool over any other club but he seems to have other plans and higher ambitions than just becoming a Liverpool legend. Of course, the move is polarizing because Liverpool look to establish a dominance, but we don't know if they actually do it or how much it lasts.
People have to understand that not long ago, even under the great Klopp, Liverpool even failed to make CL places and had to settle for Europa League football. That's not very good for a player that has high individual ambitions. To went from playing a CL final to not even qualifying in a span of 2 seasons. Very inconsistent.